The semiconductor device industry has a market driven need to continue to reduce the size of semiconductor devices such as transistors in order to obtain lower power consumption and higher performance. To reduce transistor size, the thickness of the silicon dioxide, SiO2, gate dielectric is reduced in proportion to the shrinkage of the gate length. For example, a metal-oxide-semiconductor field effect transistor (MOSFET) might use a 1.5 μm thick SiO2 gate dielectric for a gate length of 70 nm. An industry goal is to fabricate smaller, more reliable integrated circuits (ICs) for use in products such as processor chips, mobile telephones, and memory devices such as dynamic random access memories (DRAMs).
The semiconductor industry relies on the ability to reduce the dimensions of its basic devices (known as scaling), for example the silicon based MOSFET. This device scaling includes scaling the gate dielectric, which has primarily been fabricated using silicon dioxide. A thermally grown amorphous SiO2 layer provides an electrically and thermodynamically stable material, where the interface of the SiO2 layer with underlying silicon provides a high quality interface as well as superior electrical isolation properties. However, increased scaling and other requirements in microelectronic devices have created the need to use other dielectric materials as gate dielectrics, in particular dielectrics with higher dielectric constants to replace the use of various combinations of SiO2, Si3N4 and SiON. For these higher dielectric constant materials to be practical they must have the properties of high permittivity, thermal stability, high film and surface quality and smoothness, low hysteresis characteristics, low leakage current density, and long term reliability. High k films may be metal oxide unary materials such as Al2O3, CeO2, HfO2 and ZrO2, which have a single component, or binary systems such as (Y2O3)x(ZrO2)1-x, LaAlO3, and (HfO2)(Al2O3), which have two components, and so on. High k films may be single layers, or may be formed of multiple layers of different materials that act as a composite material. The high k films are preferably amorphous to maintain surface smoothness and prevent electric field concentration at sharp projections, and to minimize leakage current along crystal boundaries. There is a need in the industry to find a method of forming high k films that possess the above noted features and are practical for use in manufacturing integrated circuits (ICs).